What book has sold the most and what is in second?

It's impossible to definitively say which book has sold the most copies *ever*, as there's no central authority tracking sales across all languages, editions, and times. However, the two books most commonly cited as the best-selling are:

1. The Bible: With an estimated 5 billion copies sold over centuries, the Bible consistently tops most "best-selling books" lists. Its influence is undeniable, and its widespread distribution across languages and cultures makes it a clear contender for the top spot.

2. Quotations from Chairman Mao Tse-tung: This book, also known as the "Little Red Book", sold an estimated 800 million copies in China during the Cultural Revolution. It is considered one of the best-selling books in history, though its popularity is tied to its political context.

While the Bible and the "Little Red Book" are strong contenders, it's important to note that many other books, including "Don Quixote", "A Tale of Two Cities", and "Harry Potter" series have sold hundreds of millions of copies.